<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
 <head>
  <meta http-equiv="content-type" content="text/html; charset=UTF-8">
  <title>Raise an arbitrary precision number to another, reduced by a specified modulus</title>
<link media="all" rel="stylesheet" type="text/css" href="styles/03e73060321a0a848018724a6c83de7f-theme-base.css" />
<link media="all" rel="stylesheet" type="text/css" href="styles/03e73060321a0a848018724a6c83de7f-theme-medium.css" />

 </head>
 <body class="docs"><div class="navbar navbar-fixed-top">
  <div class="navbar-inner clearfix">
    <ul class="nav" style="width: 100%">
      <li style="float: left;"><a href="function.bcpow.html">« bcpow</a></li>
      <li style="float: right;"><a href="function.bcscale.html">bcscale »</a></li>
    </ul>
  </div>
</div>
<div id="breadcrumbs" class="clearfix">
  <ul class="breadcrumbs-container">
    <li><a href="index.html">PHP Manual</a></li>
    <li><a href="ref.bc.html">BC 数学 函数</a></li>
    <li>Raise an arbitrary precision number to another, reduced by a specified modulus</li>
  </ul>
</div>
<div id="layout">
  <div id="layout-content"><div id="function.bcpowmod" class="refentry">
 <div class="refnamediv">
  <h1 class="refname">bcpowmod</h1>
  <p class="verinfo">(PHP 5, PHP 7, PHP 8)</p><p class="refpurpose"><span class="refname">bcpowmod</span> &mdash; <span class="dc-title">Raise an arbitrary precision number to another, reduced by a specified modulus</span></p>

 </div>
 
 <div class="refsect1 description" id="refsect1-function.bcpowmod-description">
  <h3 class="title">说明</h3>
  <div class="methodsynopsis dc-description">
   <span class="methodname"><strong>bcpowmod</strong></span>(<br>&nbsp;&nbsp;&nbsp;&nbsp;<span class="methodparam"><span class="type">string</span> <code class="parameter">$num</code></span>,<br>&nbsp;&nbsp;&nbsp;&nbsp;<span class="methodparam"><span class="type">string</span> <code class="parameter">$exponent</code></span>,<br>&nbsp;&nbsp;&nbsp;&nbsp;<span class="methodparam"><span class="type">string</span> <code class="parameter">$modulus</code></span>,<br>&nbsp;&nbsp;&nbsp;&nbsp;<span class="methodparam"><span class="type">?</span><span class="type"><span class="type">int</span><span class="type"></span></span> <code class="parameter">$scale</code><span class="initializer"> = <strong><code>null</code></strong></span></span><br>): <span class="type">string</span></div>

  <p class="para rdfs-comment">
   Use the fast-exponentiation method to raise 
   <code class="parameter">num</code> to the power
   <code class="parameter">exponent</code> with respect to the modulus
   <code class="parameter">modulus</code>.
  </p>
 </div>


 <div class="refsect1 parameters" id="refsect1-function.bcpowmod-parameters">
  <h3 class="title">参数</h3>
  <p class="para">
   <dl>
    
     <dt>
<code class="parameter">num</code></dt>

     <dd>

      <p class="para">
       The base, as an integral string (i.e. the scale has to be zero).
      </p>
     </dd>

    
    
     <dt>
<code class="parameter">exponent</code></dt>

     <dd>

      <p class="para">
       The exponent, as an non-negative, integral string (i.e. the scale has to be zero).
      </p>
     </dd>

    
    
     <dt>
<code class="parameter">modulus</code></dt>

     <dd>

      <p class="para">
       The modulus, as an integral string (i.e. the scale has to be zero).
      </p>
     </dd>

    
    <dt>

<code class="parameter">scale</code></dt>
<dd>
<p class="para">此可选参数用于设置结果中小数点后的小数位数。也可通过使用
<span class="function"><a href="function.bcscale.html" class="function">bcscale()</a></span> 来设置全局默认的小数位数，用于所有函数。如果未设置，则默认为 <code class="literal">0</code>。
</p></dd>

   </dl>

  </p>
 </div>


 <div class="refsect1 returnvalues" id="refsect1-function.bcpowmod-returnvalues">
  <h3 class="title">返回值</h3>
  <p class="para">
   Returns the result as a string, or <strong><code>false</code></strong> if <code class="parameter">modulus</code>
   is <code class="literal">0</code> or <code class="parameter">exponent</code> is negative.
  </p>
 </div>


 <div class="refsect1 changelog" id="refsect1-function.bcpowmod-changelog">
  <h3 class="title">更新日志</h3>
  <table class="doctable informaltable">
   
    <thead>
     <tr>
      <th>版本</th>
      <th>说明</th>
     </tr>

    </thead>

    <tbody class="tbody">
     <tr>
      <td>8.0.0</td>
      <td>
       <code class="parameter">scale</code> is now nullable.
      </td>
     </tr>

    </tbody>
   
  </table>

 </div>


 <div class="refsect1 examples" id="refsect1-function.bcpowmod-examples">
  <h3 class="title">范例</h3>
  <p class="para">
   The following two statements are functionally identical.  The
   <span class="function"><strong>bcpowmod()</strong></span> version however, executes in
   less time and can accept larger parameters.
   <div class="informalexample">
    <div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br />$a&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">bcpowmod</span><span style="color: #007700">(</span><span style="color: #0000BB">$x</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$y</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$mod</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">$b&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">bcmod</span><span style="color: #007700">(</span><span style="color: #0000BB">bcpow</span><span style="color: #007700">(</span><span style="color: #0000BB">$x</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$y</span><span style="color: #007700">),&nbsp;</span><span style="color: #0000BB">$mod</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">//&nbsp;$a&nbsp;and&nbsp;$b&nbsp;are&nbsp;equal&nbsp;to&nbsp;each&nbsp;other.<br /><br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</code></div>
    </div>

   </div>
  </p>
 </div>


 <div class="refsect1 notes" id="refsect1-function.bcpowmod-notes">
  <h3 class="title">注释</h3>
  <blockquote class="note"><p><strong class="note">注意</strong>: 
   <p class="para">
    Because this method uses the modulus operation, numbers which are not
    positive integers may give unexpected results.
   </p>
  </p></blockquote>
 </div>


 <div class="refsect1 seealso" id="refsect1-function.bcpowmod-seealso">
  <h3 class="title">参见</h3>
  <p class="para">
   <ul class="simplelist">
    <li class="member"><span class="function"><a href="function.bcpow.html" class="function" rel="rdfs-seeAlso">bcpow()</a> - 任意精度数字的乘方</span></li>
    <li class="member"><span class="function"><a href="function.bcmod.html" class="function" rel="rdfs-seeAlso">bcmod()</a> - 任意精度数字取模</span></li>
   </ul>
  </p>
 </div>

</div></div></div></body></html>